(1) Field of the Invention
The present invention relates to a vacuum regulating valve for use in reducing the pressure of a vacuum chamber included in a physiochemical system, such as a semiconductor device fabricating system, for processing a workpiece by a chemical process.
(2) Description of the Related Art
A semiconductor substrate is subjected to a film forming process using process gasses in a vacuum chamber included in a semiconductor fabricating system to form a film on a surface of the semiconductor substrate. A vacuum regulating valve disclosed in, for example, JP-A-8-285132 is used to regulate a vacuum created in a vacuum chamber during an evacuating process for reducing pressure in the vacuum chamber prior to the film forming process and during the film forming process.
Generally, the vacuum regulating valve of this type is provided with two main ports respectively connected to the vacuum chamber and a vacuum pump. A valve seat is placed in a passage extending between the two main ports. A poppet type valve element is seated on the valve seat to close the vacuum valve and is lifted up from the valve seat to open the vacuum valve. A valve stem has one end connected to the valve element and the other end connected to a piston. The piston moves the valve stem to move the valve element for opening and closing the vacuum valve.
It is important for the vacuum regulating valve of this type to be able to intercept the flow of the process gas as perfectly as possible when the valve element is seated on the valve seat because the process gas is highly reactive and dangerous.
In some cases, the valve element is misaligned slightly with the valve stem owing to unsatisfactory machining accuracy in fabricating the components of the vacuum regulating valve and unsatisfactory assembling accuracy in assembling those components. If the valve element is thus slightly misaligned with the valve stem, the valve element comes into partial contact with the valve seat and the valve face of the valve element cannot be closely seated on the valve seat. If the valve element is thus improperly seated on the valve seat, the process gas is liable to leak.